1. Field of the Invention
The present invention relates to a method for producing a semiconductor substrate having a silicon film on an insulator substrate.
2. Description of the Related Art
As a semiconductor substrate facilitating the enhancement of performance of a semiconductor device, an SOI (Silicon On Insulator) substrate has been drawing attention (see, for example, Japanese Patent No. 3048201 or A. J. Auberton-Herve et al., “SMART CUT TECHNOLOGY: INDUSTRIAL STATUS of SOI WAFER PRODUCTION and NEW MATERIAL DEVELOPMENTS” (Electrochemical Society Proceedings Volume 99-3 (1999) p. 93-106).). This is because it is made possible to decrease a parasitic capacitance, improve a performance speed, and reduce power consumption by adopting an SOI structure to bury an oxide film under a single crystal silicon thin film.
However, because a so-called “gettering effect”, which is generally utilized in a bulk silicon substrate, can not be expected from such an SOI substrate, there is a problem in that the SOI substrate is quite susceptible to various metal contaminations in the production step thereof.
Such being the case, measures have conventionally been taken against impurities by improving the cleanliness of a process equipment or an environment. However, when a process of performing a plasma-treatment is adopted to secure a bonding strength in the case of bonding an insulator substrate and a silicon substrate at a low temperature, metal impurities are prone to accumulate in a bonding interface at a high density with the progress of the plasma-treatment. Therefore the mere clean-up of the plasma-treatment environment is not enough as the measures against the metal contaminations.